Comparison of phenol, nitrogen and oxygen demand removal in constructed wetlands with gravel- and rice husk-based media
| dc.contributor.author | Tee, Heng Chong | |
| dc.date.accessioned | 2014-11-03T02:35:19Z | |
| dc.date.available | 2014-11-03T02:35:19Z | |
| dc.date.issued | 2006 | |
| dc.description | Master | en_US |
| dc.description.abstract | This study aims to investigate the potential of raw rice husks to be used as an alternative media in constructed wetlands to treat phenol-containing domestic wastewater. The role of wetland vegetation in the removal of nitrogen, oxygen demand and phenol, and the effect of phenol on nitrogen and oxygen demand removal in constructed wetlands were also studied. Four laboratory-scale horizontal subsurface-flow constructed wetland units were built and were operated outdoors. Two of the wetland units were filled with pea gravel and the other two with mainly raw rice husks as wetland media to a depth 0.60 m. One unit of each type of constructed wetland was planted with cattail (Typha latifolia). The units were initially fed with domestic wastewater and operated at a nominal hydraulic retention time of 7 days. After the cattail plants had attained maturity, the concentrations of ammonical nitrogen (AN), total nitrogen kjeldhal (TKN) and chemical oxygen demand (COD) were monitored at the inlet, outlet and the intermediate sampling points at the depths of 0.15 dan 0.45 m for six months. Subsequently, the wetland units were fed with the same domestic wastewater spiked with increasing phenol concentrations at 100, 300 and 500 mg/L for the durations of 30, 74 and 198 days, respectively. During these periods, phenol, AN, TKN and COD concentrations at those sampling positions mentioned above were monitored. The results showed that planted wetland units were more efficient than unplanted wetland units in nitrogen removal before and after the addition of phenol. This indicated that wetland plants play an important role in nitrogen removal. The results also showed that, irrespective of planted or unplanted, there was nearly total phenol removal in the gravel- and rice husk-based wetland units when 300 mg/L phenol was added. However, at 500 mg/L phenol, the percentages of phenol removal for unplanted gravel- and rice husk-based wetland units deteriorated to 18 and 21%, respectively, whereas the planted units yielded 68 and 100%, respectively. In the presence of phenol, the reduction of AN and TKN removal efficiencies was observed in both types of planted and unplanted wetland units but the effect was greater in the unplanted units indicating that wetland vegetations play a role in reducing the inhibitory effect of phenol. As the values of COD obtained in this study were dominated by the present of phenol, the effect of phenol on COD cannot be determined. From the kinetic study, the rate of degradation for phenol in aerobic condition was found to be faster than that in anoxic condition. The results of the GCMS study proved that phenol was mineralized according to the pathway: o-cresol → benzoquinone → cis-cis mucanoic acid → succinic acid → etanoic acid and finally water and carbon dioxide as the final products. The SOUR study indicated that phenol and o-cresol were most toxic compounds to the nitrifying bacteria. This research shows that raw rice husks can be used as an alternative media in constructed wetlands. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/321 | |
| dc.language.iso | en | en_US |
| dc.subject | Biological science | en_US |
| dc.subject | Constructed wetlands | en_US |
| dc.subject | Rice husk-based media | en_US |
| dc.title | Comparison of phenol, nitrogen and oxygen demand removal in constructed wetlands with gravel- and rice husk-based media | en_US |
| dc.type | Thesis | en_US |
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